The present invention relates to a method of and to an apparatus for making and/or manipulating streams of tobacco, filter material for tobacco smoke and other types of fibrous material. More particularly, the invention relates to improvements in a method of and in an apparatus for making and/or manipulating streams of fibrous material in machines which can be utilized with particular advantage for the production of rod-shaped smokers' products. Still more particularly, the invention relates to the making and/or manipulating of streams of fibrous material preparatory to further processing of the streams, especially preparatory to draping of such streams into running webs of cigarette paper, tipping paper, artificial cork and/or like wrapping material.
It is known to build a stream of comminuted tobacco, such as a stream of tobacco shreds, in a cigarette making machine by directing tobacco particles against one side of a moving endless foraminous belt conveyor the other side of which advances along a suction chamber so that the one side attracts the particles and causes them to form a tobacco stream. The fully grown stream is thereupon trimmed or equalized (i.e., the surplus is removed therefrom) prior to draping the resulting rod-like filler into a web of cigarette paper or the like so that the web and the filler form a continuous rod which is thereupon subdivided into plain cigarettes of unit length or multiple unit length. The particles are supplied by the distributor of the cigarette making machine, often in the form of a shower whose particles ascend toward the underside of the lower reach of the belt conveyor. The lower reach of the belt conveyor is caused to advance in a channel which is flanked by two downwardly extending sidewalls and by a perforated top wall which forms part of a suction chamber and is adjacent to the upper side of the lower reach. The suction chamber ensures that the ascending particles (such as tobacco shreds) adhere to the underside and travel with the lower reach of the belt conveyor toward the trimming or equalizing station and thereupon to the station where the trimmed stream (i.e., the filler) is transferred onto a running web of wrapping material at or ahead of a wrapping station.
The building of a tobacco stream at the underside of the lower reach of a foraminous belt conveyor is desirable on the ground that the filler (trimmed stream) can be conveniently deposited on the running web of wrapping material at or immediately ahead of the wrapping station. On the other hand, the building of the stream at the underside of the lower reach of a foraminous belt conveyor also presents problems because the particles of fibrous material must be propelled upwardly by streams of compressed air, by mechanical propelling means and/or by suction. Reference may be had to commonly owned U.S. Pat. No. 4,175,570 to Heitmann and/or to commonly owned U.S. Pat. No. 4,185,644 to Heitmann et al. If the stream of fibrous material is formed in the circumferential groove of a suction wheel (see, for example, the disclosure of the commonly owned U.S. Pat. No. 4,004,593 to Kaeding et al.), the fully grown stream must be transferred to the underside of the lower reach of a foraminous belt conveyor prior to transfer onto the upper side of the running web of wrapping material. All of the above outlined techniques are costly, complex and entail undesirable and unpredictable deformation of the stream in a manner which can affect the quality of the ultimate product. In many instances, the simplest and most reliable way of forming a continuous stream of tobacco shreds or the like would be to simply shower the particles onto the upper side of the upper reach of a foraminous belt conveyor; however, this presents problems in connection with the transfer of the thus formed stream onto the upper side of a running web of wrapping material because the upper reach of the belt conveyor is disposed below the fully grown stream. In other words, it is presently necessary to transfer the fully grown stream onto a further foraminous belt conveyor in such a way that the tobacco stream is adjacent and adheres to the underside of the further foraminous conveyor ahead of the wrapping station and ahead of the location where successive increments of the stream come in contact with the web of wrapping material. The utilization of a further foraminous belt conveyor downstream of the stream building or growing zone contributes to the length and complexity of the rod making machine and establishes an additional possibility of adversely affecting the appearance, density and/or other desirable characteristics of the stream prior to wrapping.